As shown in FIGS. 1 and 2, in the conventional gill C and bobinoir D, a sliver 12 is controlled by needles 10a of a follower 10 or needles 11a of a porcupine roller 11 to impart a draft to the sliver 12.
In a recently developed draft apparatus in which high drafting is made possible while increasing the drafting speed, for example, as shown in FIG. 3, an intermediate roller 13 comprising a balloon rollers 13a and a lower apron 13b is arranged, or as shown in FIG. 4, an intermediate roller 14 comprising double aprons 14a and 14b is arranged as a substitute for the follower or porcupine roller. These high drafting operations are performed without using needles, whereby the draft ratio and drafting speed can be increased.
However, these high draft apparatuses are defective in the following points as compared with the draft apparatus comprising a follower or porcupine roller.
(1) The evenness of a sliver is low and yarn breakages are readily caused in a spinning frame.
(2) Defects of a sliver caused at the preceding steps are not substantially eliminated but are sometimes worsened.
(3) Occurence of unevenness by joining of slivers in not prevented at all.
Each of the recently developed high draft apparatuses is of an apron type or similar type as shown in FIGS. 3 or 4, and it is an indispensable requirement that an ideal and good sliver should be supplied. However, incorporation of a defective sliver or a sliver having defects cannot practically be avoided, and the above-mentioned defects (1) and (2) are caused in the practical operation. Namely, when such defective sliver is supplied, abnormal expansion of the sliver is more prominent than in the conventional low draft apparatus, and yarn breakages are frequently caused in a spinning frame, resulting in reduction of the yarn quality.
The defect (3) will now be described. As shown in FIG. 5, before a sliver 12 supplied from a can 15 is completely consumed, the top end 212a of a sliver 212 taken out from a full can 215 which is let to stand by for the subsequent supply is partially lapped on the rear end 12a of the sliver 12 of the can 15 and joining is performed. Since needles are not nused in the high draft apparatus as pointed out herein-before, the formed joint is not normally drafted but a defect of unevenness appears on the joint, and this uneven portion should be removed afterwards. Because of this operation loss, the effects of increasing the operation speed and the productivity cannot satisfactorily be attained, and this disadvantage is especially serious when an automatic doffing apparatus is arranged.
Unevenness of sliver of this type cannot be checked by the naked eye and the sliver is directly forwarded to a spinning frame, and when an uneven yarn is spun and a fabric is formed by knitting or weaving, this defect is first found out and the poor quality becomes a problem. One of the reasons why adoption of a high draft bobinoir is hesitated is a risk of this poor quality.